Less is more.
Picture this, driving down the road and you pass a vehicle that has more words on it than you have hair on your head. You just cannot read it. When designing your vehicle lettering, pick the best selling or hottest items or services you provide and use only those few. Website is important and also phone number of course.
Something else to think about is to have a tagline that really describes what you do or sell. That way you simplify it even more. Here is an example: My logo (RPM Graphics), Signs That Drive Marketing Performance, 763-422-1790, www.rpmgraphics-mn.com. That pretty much says it all. I really do not have to expand on that at all. They will call or check out my website. Then I will expand on what we can provide them with.
-Jenny Anderson-Giese, RPM Graphics has been in business for 10 years. Jenny also has 20+ years graphic design experience.